1. Technical Field
The disclosure relates to cooling fans, and particularly to a cooling fan having an impeller which can have a reduced noise when the impeller rotates.
2. Description of Related Art
It is well known that heat is generated by electronic components such as integrated circuit chips during operation thereof. If the heat is not efficiently removed, these electronic components may suffer damage. Thus, cooling fans are often used to cool the electronic components.
A typical cooling fan includes a housing, a cover on the housing, and a stator and an impeller received in a space defined between the housing and the cover. The impeller includes a hub and a plurality of blades extending radially and outwardly from the hub. Each of the blades includes a windward surface and a leeward surface opposite to the windward surface. When the cooling fan operates, the blades of the impeller drive air therebetween to rotate to generate forced airflow. The airflow flows towards free ends of the blades due to centrifugal force and then separates from the blades adjacent to free ends of the leeward surfaces. The airflow separated from the leeward surfaces generates a vortex adjacent to the free ends of the blades. The vortex generates noise which makes a user near the cooling fan feel uncomfortable.
What is needed, therefore, is an impeller and a cooling fan which can overcome the described limitations.